Submerged fermentation with single or mixed metal ions as inducers was used for laccase production from white rot fungi. Mixed metal ions were used for the first time as inducers for Pleurotus ostreatus and Flammulina velutipes to enhance laccase activity. The maximum laccase activity from P. ostreatus in basal media, metal ion media 1 containing copper ion, metal ion media 2 containing manganese ion, metal ion media 3 containing manganese and copper ions, metal ion media 4 containing ferrous ion, metal ion media 5 containing manganese and ferrous ions, metal ion media 6 containing ferrous and copper ions, and metal ion media 7 containing manganese, copper and ferrous ions were, respectively, approximately 21.5-fold, 4.7-fold, 14.9-fold, 16.9-fold, 4.0-fold, 11.0-fold, 12.7-fold, and 24.8-fold higher than that from F. velutipes. The combination of copper and manganese ions as inducers was superior to that of a single copper ion or manganese ion. The maximum laccase activity of P. ostreatus rose in media containing manganese and copper ions. The single copper ion as the inducer for enhancing laccase activity was more suitable for F. velutipes. These findings are helpful in selecting the appropriate single metal ion or mixed metal ions to enhance laccase activity.
Microbial fuel cells, a renewable energy technology for bio-electricity generation: A mini-review